SIDE EFFECTS

Respiratory

CHRONIC PULMONARY REACTIONS MAY OCCUR GENERALLY IN
PATIENTS WHO HAVE RECEIVED CONTINUOUS TREATMENT FOR SIX MONTHS OR LONGER.
MALAISE, DYSPNEA ON EXERTION, COUGH, AND ALTERED PULMONARY FUNCTION ARE COMMON
MANIFESTATIONS WHICH CAN OCCUR INSIDIOUSLY. RADIOLOGIC AND HISTOLOGIC FINDINGS
OF DIFFUSE INTERSTITIAL PNEUMONITIS OR FIBROSIS, OR BOTH, ARE ALSO COMMON
MANIFESTATIONS OF THE CHRONIC PULMONARY REACTION. FEVER IS RARELY PROMINENT.

THE SEVERITY OF CHRONIC PULMONARY REACTIONS AND THEIR
DEGREES OF RESOLUTION APPEAR TO BE RELATED TO THE DURATION OF THERAPY AFTER THE
FIRST CLINICAL SIGNS APPEAR. PULMONARY FUNCTION MAY BE IMPAIRED PERMANENTLY,
EVEN AFTER CESSATION OF THERAPY. THE RISK IS GREATER WHEN CHRONIC PULMONARY
REACTIONS ARE NOT RECOGNIZED EARLY.

In subacute pulmonary reactions, fever and eosinophilia
occur less often than in the acute form. Upon cessation of therapy, recovery
may require several months. If the symptoms are not recognized as being
drug-related and nitrofurantoin therapy is not stopped, the symptoms may become
more severe.

Acute pulmonary reactions are commonly manifested by
fever, chills, cough, chest pain, dyspnea, pulmonary infiltration with
consolidation of pleural effusion on X-ray, and eosinophilia. Acute reactions
usually occur within the first week of treatment and are reversible with
cessation of therapy. Resolution often is dramatic. (see WARNINGS)

Hematologic

Miscellaneous

As with other antimicrobial agents, superinfections
caused by resistant organisms, e.g., Pseudomonas species or Candida species,
can occur. There are sporadic reports of Clostridium difficile superinfections,
or pseudomembranous colitis, with the use of nitrofurantoin.

DRUG INTERACTIONS

Antacids containing magnesium trisilicate, when
administered concomitantly with nitrofurantoin, reduce both the rate and extent
of absorption. The mechanism for this interaction probably is adsorption of
nitrofurantoin onto the surface of magnesium trisilicate.

Uricosuric drugs, such as probenecid and sulfinpyrazone,
can inhibit renal tubular secretion of nitrofurantoin. The resulting increase
in nitrofurantoin serum levels may increase toxicity, and the decreased urinary
levels could lessen its efficacy as a urinary tract antibacterial.

Drug/laboratory Test Interactions

As a result of the presence of nitrofurantoin, a
false-positive reaction for glucose in the urine may occur. This has been observed
with Benedict's and Fehling's solutions but not with the glucose enzymatic
test.